1. Field of the Invention
The present invention relates to a chair utilizing concurrence between descent of a seat and back-and-forth swing motion of a backrest, which is preferably used, in particular, as a revolving office chair.
2. Prior Art
Heretofore, various types of chairs have been proposed which are so constructed as to utilize concurrence between descent of a seat and back-and-forth swing motion of a backrest, and some of them have been practically used.
Such conventional chairs, however, which utilize concurrence between descent of a seat and back-and-forth swing motion of a backrest, inevitably have complicated structures due to their functions. Accordingly, most of the chairs having such functions and structures have their operative portions entirely covered with so-called outer shells.
When a chair has its seat bottom and backrest rear covered with an outer shell made of a synthetic resin, the chair has an awkwardly thick profile, in particular, in a portion below the seat, thereby leading to lack of lightness. Further, the chair is disadvantageously restricted in its design owing to the seat bottom and the backrest being entirely covered with the outer shell. In addition, it has a complicated structure and constituent members thereof are densely arranged. Consequently, manufacture thereof is, of course, not easy and yet maintenance thereof is not easy.